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Frederic Barlat - One of the best experts on this subject based on the ideXlab platform.
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calibration of a Strain Path Change model for a dual phase steel
International Journal of Mechanical Sciences, 2021Co-Authors: Diane Herault, Sandrine Thuillier, Shinyeong Lee, Pierreyves Manach, Frederic BarlatAbstract:Abstract Dual phase steels are largely used to form automotive structural parts by deep drawing involving complex loading Paths, which influence the material mechanical behavior and formability, as well as subsequent service life. The aim of this paper is to investigate the calibration of a Strain Path Change model from an experimental database involving simple shear tests. The enhanced Homogeneous Anisotropic Hardening (e-HAH) is an advanced constitutive model that can take account of the Strain Path Change influence on the material behavior by using a stress-based indicator. The performance of such a model depends highly on the material parameter identification and the experimental database. The mechanical behavior of a dual phase steel DP600 is first characterized under different linear Strain Paths, uniaxial and biaxial tension and simple shear, in order to quantify the initial anisotropy. Then, the influence of Strain Path Changes on the material behavior is investigated during sequences involving simple shear, uniaxial tension and compression. Finally, the parameters of e-HAH model are identified and the influence of the experimental database on the optimised parameters is highlighted with the use of different Strain Paths and different Strain ranges.
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Hardening behavior and texture evolution of TWIP steel during Strain Path Change
IOP Conference Series: Materials Science and Engineering, 2015Co-Authors: Wei Wen, M. Borodachenkova, Frederic Barlat, António Pereira, José GrácioAbstract:Polycrystal materials exhibit large Changes in the flow stress and hardening behavior during the Strain Path Change. Such Changes are related with the crystallographic texture anisotropy and the rearrangement of dislocation structure during the pre-loading. These effects have been captured by a dislocation hardening model embedded in the visco-plastic selfconsistent (VPSC) model. In this work, the texture evolution and mechanical behavior of TWIP steel during the Strain Path Change are investigated. The experimental studies are carried out on rolled TWIP steel sheet. The mechanical responses are obtained under tensile tests along rolling direction, followed by tension along the directions with 0° and 90° from the pre-loading direction. The simulated results of Strain-stress curves and the texture evolution are in good agreement with the experimental data.
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stress update algorithm for enhanced homogeneous anisotropic hardening model
Computer Methods in Applied Mechanics and Engineering, 2015Co-Authors: Hyuk Jong Bong, Frederic BarlatAbstract:Abstract A stress integration algorithm is provided for a novel homogeneous-yield-function-based anisotropic hardening (HAH) model. The new model is an extension of the original HAH model that describes cross-hardening or softening of a sheet metal under an orthogonal Strain Path Change. A semi-explicit integration scheme for the stress update is utilized to efficiently handle the gradient of the distorted yield surface during complex Strain Path Changes, as originally proposed by Lee et al. (2012). Validations of the algorithm developed were conducted by comparing the predicted stress–Strain curves of dual-phase (DP) 780 and extra-deep-drawing-quality (EDDQ) steels with experimental stress–Strain responses observed under cross-loading conditions. Finally, the accuracy of the proposed finite element (FE) formulations was assessed by r -value prediction and preparation of iso-error maps.
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continuous Strain Path Change simulations for sheet metal
Computational Materials Science, 2014Co-Authors: Jinhwan Kim, Frederic Barlat, Myounggyu LeeAbstract:Abstract The plastic behavior of a material undergoing continuous Strain Path Changes, from plane Strain to simple shear, was simulated for a mild steel. A distortional hardening model was employed to capture the Bauschinger effect and latent hardening. The simulations were conducted by direct application of the constitutive equations with simple boundary conditions and by using a finite element code in which the distortional hardening model was previously implemented. Depending on the rate of Path Change, the simulations resulted in different combinations of plastic responses including the Bauschinger effect, transient hardening, flow stress overshooting and Strain hardening stagnation. The simulated stress–Strain curves were found to be in good agreement with experimental results published by van Riel and van den Boogaard (2007).
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numerical simulation of the mechanical response during Strain Path Change application to zn alloys
Procedia Engineering, 2014Co-Authors: M. Borodachenkova, Frederic Barlat, Wei Wen, A B Pereira, José GrácioAbstract:The microstructure-based hardening model (Beyerlein and Tome, 2007), that accounts for the dislocation reversal-related mechanisms and the cut-through effect, is extended to HCP metals. This model, which is embedded in the visco-plastic self-consistent framework, is applied in this work to predict the mechanical response of Zn alloy during Strain Path Change. The predicted mechanical behavior and texture evolution during pre-loading and reloading is in good agreement with experimental observations. The Change in hardening behavior after reloading is well reproduced by this model. The contributions of the different mechanisms are also analyzed.
Mitsutoshi Kuroda - One of the best experts on this subject based on the ideXlab platform.
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Forming Limit Stresses of Sheet Metal under Proportional and Combined Loadings
AIP Conference Proceedings, 2005Co-Authors: Kengo Yoshida, Mitsutoshi KurodaAbstract:The effects of changing Strain Paths on forming limit stresses of sheet metals are investigated using the Marciniak‐Kuczynski model. Forming limits are analyzed for proportional loading and two types of combined loadings: combined loading which includes unloading between the first and second loadings and that which includes an abrupt Strain Path Change without unloading between the first and second loadings. The forming limit stress curves in stress space calculated for the combined loading with unloading are in good agreement with those calculated for the proportional loading, while the forming limit curves in Strain space are strongly dependent on the Strain Paths. The forming limit stresses calculated for combined loading with an abrupt Strain Path Change, however, do not coincide with those calculated for proportional loading. The Strain Path dependence of the forming limit stresses is discussed in detail.
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yield locus and work hardening behavior of a thin walled steel tube subjected to combined tension internal pressure
Journal De Physique Iv, 2003Co-Authors: Toshihiko Kuwabara, Mitsutoshi Kuroda, Mantaro Ishiki, Susumu TakahashiAbstract:A servo-controlled tension-internal pressure testing machine for metal tubes is newly developed. The testing machine is capable of giving arbitrary stress or Strain Paths to a tubular specimen using an electrical, closed-loop feedback control system. Biaxial stress experiments are carried out for low carbon steel tubes. Contours of equal plastic work are determined in the principal stress space for linear stress Paths. The work contours are found to keep a geometry almost identical to Hosford's yield locus. The directions of measured incremental plastic Strain vectors are in good agreement with those of local outward normals to Hosford's yield locus. Moreover, a subsequent yield locus following equibiaxial tension is measured without unloading using the abrupt Strain Path Change method proposed by Kuroda and Tvergaard [Acta Mater. 47 (1999) 3879-3890]. A yield vertex is successfully observed at the point of loading, and non-normality behavior of the plastic Strain rate vector for non-proportional loading is confirmed.
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use of abrupt Strain Path Change for determining subsequent yield surface experimental study with metal sheets
Acta Materialia, 2000Co-Authors: Toshihiko Kuwabara, Mitsutoshi Kuroda, Viggo Tvergaard, K NomuraAbstract:A basic idea for a method for determining the subsequent yield surface in the vicinity of a current loading point by using an abrupt Strain Path Change has been proposed recently by Kuroda and Tvergaard (Acta mater., 1999, 47, 3879). The proposed method is applied to real experimental studies. In a biaxial tensile testing apparatus, a cruciform specimen is used, with the Strains measured by a biaxial-Strain gauge. Then, with the hydraulic pressure of two sets of opposing hydraulic cylinders servo-controlled independently, the testing apparatus can be used to prescribe an abrupt Change of the Strain Path. Both a cold-rolled steel sheet and an aluminum alloy sheet are investigated. The differences between the yield surface shapes found by the Strain Path Change procedure and the shapes found by probing the yield points from the elastic region are shown and discussed for different cases.
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effect of Strain Path Change on limits to ductility of anisotropic metal sheets
International Journal of Mechanical Sciences, 2000Co-Authors: Mitsutoshi Kuroda, Viggo TvergaardAbstract:Abstract Localized necking in thin metal sheets is analyzed by using the M–K-model approach, and the effect of a number of different non-proportional Strain Paths prior to the occurrence flow localization are considered. The analyses account for plastic anisotropy, using four different anisotropic plasticity models to fit a set of experimental data for cold-rolled steel sheet. The predicted forming limit diagrams show strong dependence on whether or not the load on the sheet is removed between two load steps on a non-proportional Strain Path. This dependence is investigated in detail for one of the anisotropic plasticity models, and it is shown that elastic Straining plays a large role, as the stresses quickly move from one point of the yield surface to another. When the load is removed between steps, the stress point moves in a different manner, which results in quite different flow localization response.
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use of abrupt Strain Path Change for determining subsequent yield surface illustrations of basic idea
Acta Materialia, 1999Co-Authors: Mitsutoshi Kuroda, Viggo TvergaardAbstract:Abstract For elastic–plastic materials, a new method is proposed for determining the shape of the subsequent yield surface in the vicinity of a current loading point. A proportional Strain Path is prescribed until the loading point of interest has been reached, then an abrupt Strain Path Change is prescribed, which makes the stress point move quickly along the yield surface. It is assumed that a closed-loop testing machine is used for the experiment, so that the Strain Path can be prescribed according to Strain gauge measurements. Relative to the standard method of determining yield surface shapes by probing in many different stress directions from the elastic region, using some chosen plastic Strain offset, the main advantage of the proposed method is that elastic unloading is not needed prior to tracing the yield surface. The method is illustrated here by a few analyses, first for the simplest flow theory of plasticity, and subsequently for crystal plasticity, using the Taylor model to represent a polycrystal.
Viggo Tvergaard - One of the best experts on this subject based on the ideXlab platform.
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use of abrupt Strain Path Change for determining subsequent yield surface experimental study with metal sheets
Acta Materialia, 2000Co-Authors: Toshihiko Kuwabara, Mitsutoshi Kuroda, Viggo Tvergaard, K NomuraAbstract:A basic idea for a method for determining the subsequent yield surface in the vicinity of a current loading point by using an abrupt Strain Path Change has been proposed recently by Kuroda and Tvergaard (Acta mater., 1999, 47, 3879). The proposed method is applied to real experimental studies. In a biaxial tensile testing apparatus, a cruciform specimen is used, with the Strains measured by a biaxial-Strain gauge. Then, with the hydraulic pressure of two sets of opposing hydraulic cylinders servo-controlled independently, the testing apparatus can be used to prescribe an abrupt Change of the Strain Path. Both a cold-rolled steel sheet and an aluminum alloy sheet are investigated. The differences between the yield surface shapes found by the Strain Path Change procedure and the shapes found by probing the yield points from the elastic region are shown and discussed for different cases.
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effect of Strain Path Change on limits to ductility of anisotropic metal sheets
International Journal of Mechanical Sciences, 2000Co-Authors: Mitsutoshi Kuroda, Viggo TvergaardAbstract:Abstract Localized necking in thin metal sheets is analyzed by using the M–K-model approach, and the effect of a number of different non-proportional Strain Paths prior to the occurrence flow localization are considered. The analyses account for plastic anisotropy, using four different anisotropic plasticity models to fit a set of experimental data for cold-rolled steel sheet. The predicted forming limit diagrams show strong dependence on whether or not the load on the sheet is removed between two load steps on a non-proportional Strain Path. This dependence is investigated in detail for one of the anisotropic plasticity models, and it is shown that elastic Straining plays a large role, as the stresses quickly move from one point of the yield surface to another. When the load is removed between steps, the stress point moves in a different manner, which results in quite different flow localization response.
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use of abrupt Strain Path Change for determining subsequent yield surface illustrations of basic idea
Acta Materialia, 1999Co-Authors: Mitsutoshi Kuroda, Viggo TvergaardAbstract:Abstract For elastic–plastic materials, a new method is proposed for determining the shape of the subsequent yield surface in the vicinity of a current loading point. A proportional Strain Path is prescribed until the loading point of interest has been reached, then an abrupt Strain Path Change is prescribed, which makes the stress point move quickly along the yield surface. It is assumed that a closed-loop testing machine is used for the experiment, so that the Strain Path can be prescribed according to Strain gauge measurements. Relative to the standard method of determining yield surface shapes by probing in many different stress directions from the elastic region, using some chosen plastic Strain offset, the main advantage of the proposed method is that elastic unloading is not needed prior to tracing the yield surface. The method is illustrated here by a few analyses, first for the simplest flow theory of plasticity, and subsequently for crystal plasticity, using the Taylor model to represent a polycrystal.
Myounggyu Lee - One of the best experts on this subject based on the ideXlab platform.
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Influence of Evolution in Anisotropy During Strain Path Change on Failure Limits of Sheet Metals
Metals and Materials International, 2020Co-Authors: Kaushik Bandyopadhyay, Shamik Basak, Hongjin Choi, Sushanta K. Panda, Myounggyu LeeAbstract:Effects of evolution in anisotropy during plastic deformation under Strain Path Changes on the formability and failure were investigated in the present study. The evolution in anisotropic property of the extra deep drawing steel was considered by implementing the non-quadratic anisotropic yield function Yld2000-2d as a function of effective plastic Strain, and the corresponding forming behaviour in two-step forming processes was analysed. For the Strain Path effect, pre-Strain was applied under biaxial mode using Marciniak in-plane stretch forming set-up, followed by the secondary deformation using the out-of-plane stretch forming tool. For failure prediction of the proposed two-step forming, different failure limit approaches were investigated. First, a Strain based forming limit diagram (FLD), proposed as the Marciniak–Kuczynski model was modified to include the evolution in anisotropic yield function. The dynamic shift in FLD was also determined by taking Strain Path Change into consideration. In addition, the influence of evolution of yield function on the Strain Path independent failure limit criteria was also assessed in terms of stress based forming limit diagram. Finally, the prediction accuracy of the failure limit criteria was compared among different models in terms of failure location and limiting dome height (LDH). It was observed that the incorporation of evolution in anisotropic yield surface improved the prediction of formability in terms of the LDH and Strain distribution for the investigated material. Graphic Abstract
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continuous Strain Path Change simulations for sheet metal
Computational Materials Science, 2014Co-Authors: Jinhwan Kim, Frederic Barlat, Myounggyu LeeAbstract:Abstract The plastic behavior of a material undergoing continuous Strain Path Changes, from plane Strain to simple shear, was simulated for a mild steel. A distortional hardening model was employed to capture the Bauschinger effect and latent hardening. The simulations were conducted by direct application of the constitutive equations with simple boundary conditions and by using a finite element code in which the distortional hardening model was previously implemented. Depending on the rate of Path Change, the simulations resulted in different combinations of plastic responses including the Bauschinger effect, transient hardening, flow stress overshooting and Strain hardening stagnation. The simulated stress–Strain curves were found to be in good agreement with experimental results published by van Riel and van den Boogaard (2007).
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extension of quasi plastic elastic approach to incorporate complex plastic flow behavior application to springback of advanced high strength steels
International Journal of Plasticity, 2013Co-Authors: Jinwoo Lee, Frederic Barlat, Jeongyeon Lee, R H Wagoner, Kwansoo Chung, Myounggyu LeeAbstract:Materials modeling and numerical formulations were conducted to describe the complex material behavior upon Strain Path Change in order to enhance the prediction accuracy of springback in advanced high strength steels (AHSS). An approach without kinematic hardening rule, or the homogeneous anisotropic hardening (HAH) model, was incorporated to the newly conceived quasi-plastic–elastic Strain (QPE) formulations. The HAH model is able to capture complex plastic flow behavior of sheet metals such as the Bauschinger effect, transient behavior, work-hardening stagnation and permanent softening. The QPE approach was developed to reproduce the nonlinear elastic behavior during unloading and reloading. The two models were independently validated for predicting springback, with better performance than conventional constitutive models. In this study, the two models are combined and extended to enhance the prediction capability of springback in AHSS. For this purpose, fully implicit numerical algorithms were re-formulated to link the two modeling approaches using general anisotropic yield function and hardening for shell element. The original model was only valid for continuum isotropic element with analytical stress integration procedure. Simulations of 2D draw bending test were performed to validate the developed approach for two AHSS, DP780 and TRIP780, sheets. The springback prediction was significantly improved if most of the complex material behavior relating to elasticity and plasticity were taken into account in the finite element simulations.
Cristian Teodosiu - One of the best experts on this subject based on the ideXlab platform.
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finite element modeling of plastic anisotropy induced by texture and Strain Path Change
International Journal of Plasticity, 2003Co-Authors: Eric Hoferlin, Albert Van Bael, Paul Van Houtte, Cristian TeodosiuAbstract:Abstract Consideration of plastic anisotropy is essential in accurate simulations of metal forming processes. In this study, finite element (FE) simulations have been performed to predict the plastic anisotropy of sheet metals using a texture- and microstructure-based constitutive model. The effect of crystallographic texture is incorporated through the use of an anisotropic plastic potential in Strain-rate space, which gives the shape of the yield locus. The effect of dislocation is captured by use of a hardening model with four internal variables, which characterize the position and the size of the yield locus. Two applications are presented to evaluate the accuracy and the efficiency of the model: a cup drawing test and a two-stage pseudo-orthogonal sequential test (biaxial stretching in hydraulic bulging followed by uniaxial tension), using an interstitial-free steel sheet. The experimental results of earing behavior in the cup drawing test, maximum pressure and Strain distribution in bulging, and transient hardening in the sequential test are compared against the FE predictions. It is shown that the current model is capable of predicting the plastic anisotropy induced by both the texture and the Strain-Path Change. The relative significance of texture and Strain-Path Change in the predictions is discussed.
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a theoretical investigation of the influence of dislocation sheets on evolution of yield surfaces in single phase b c c polycrystals
Journal of The Mechanics and Physics of Solids, 2002Co-Authors: Bart Peeters, Paul Van Houtte, Cristian Teodosiu, Surya R Kalidindi, E AernoudtAbstract:Abstract Accurate and reliable predictions of yield surfaces and their evolution with deformation require a better physical representation of the important sources of anisotropy in the material. Until recently, the most physical approach employed in the current literature has been the use of polycrystalline deformation models, where it is assumed that crystallographic texture is the main contributor to the overall anisotropy. However, recent studies have revealed that the grain-scale mesostructural features (e.g. cell-block boundaries) may have a large impact on the anisotropic stress–Strain behaviour, as evidenced during Strain-Path Change tests (e.g. cross effect, Bauschinger effect). In previous papers, the authors formulated an extension of the Taylor-type crystal plasticity model by incorporating some details of the grain-scale mesostructural features. The main purpose of this paper is to study the evolution of yield surfaces in single-phase b.c.c. polycrystals during deformation and Strain-Path Changes using this extended crystal plasticity model. It is demonstrated that the contribution of the grain-scale substructure in these metals on yield loci is comparable in magnitude to the effects caused by the differences in texture. Furthermore, it is shown that the shape of yield loci cannot be predicted accurately by the traditional polycrystalline deformation model with equal slip hardening. The trends predicted by the extended crystal plasticity model are in much better agreement with the experimental evidence reported in the literature than those represented in classical treatments by isotropic and kinematic hardening.
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work hardening softening behaviour of b c c polycrystals during changing Strain Paths i an integrated model based on substructure and texture evolution and its prediction of the stress Strain behaviour of an if steel during two stage Strain Paths
Acta Materialia, 2001Co-Authors: Bart Peeters, Cristian Teodosiu, Surya R Kalidindi, Marc Seefeldt, P Van Houtte, E AernoudtAbstract:Abstract For many years polycrystalline deformation models have been used as a physical approach to predict the anisotropic mechanical behaviour of materials during deformation, e.g. the r -values and yield loci. The crystallographic texture was then considered to be the main contributor to the overall anisotropy. However, recent studies have shown that the intragranular microstructural features influence strongly the anisotropic behaviour of b.c.c. polycrystals, as revealed by Strain-Path Change tests (e.g. cross effect, Bauschinger effect). This paper addresses a method of incorporating dislocation ensembles in the crystal plasticity constitutive framework, while accounting for their evolution during changing Strain Paths. Kinetic equations are formulated for the evolution of spatially inhomogeneous distributions of dislocations represented by three dislocation densities. This microstructural model is incorporated into a full-conStraints Taylor model. The resulting model achieves for each crystallite a coupled calculation of slip activity and dislocation structure evolution, as a function of the crystallite orientation. Texture evolution and macroscopic flow stress are obtained as well. It is shown that this intragranular–microstructure based Taylor model is capable of predicting quantitatively the complex features displayed by stress–Strain curves during various two-stage Strain Paths.
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prediction of forming limit Strains under Strain Path Changes application of an anisotropic model based on texture and dislocation structure
International Journal of Plasticity, 1998Co-Authors: Shunji Hiwatashi, Albert Van Bael, Paul Van Houtte, Cristian TeodosiuAbstract:Abstract Strain-Path Changes strongly influence the forming limit Strains of sheet metals. The value of the limit Strains is greatly affected by material-related effects such as initial anisotropy, transient. hardening, Bauschinger effect and cross hardening. A model which can describe these mechanical behaviours has been developed on the physical basis of texture and dislocation structure, and applied in conjunction with the Marciniak-Kuczynski analysis of the forming limit Strains. The results are represented in forming limit diagrams (FLDs) in which the forming limit Strains are indicated. The calculation successfully predicts some of the experimental tendencies which cannot be reproduced by conventional phenomenological models. Furthermore, the model has been used to discuss the effects of texture and dislocation structure on the FLDs. Especially, it is suggested that transient hardening caused by the latent part of the persistent dislocation structure significantly reduces the forming limit Strain for a Strain-Path Change from equi-biaxial stretching to uniaxial tension.